KR100315571B1 - Method for preparing 1,2-dichloroethane and apparatus for performing such methods - Google Patents

Abstract

During the reaction of ethylene with chlorine to give 1,2-dichloroethane (EDC), high purity EDC is obtained by using the catalytic component sodium chloride-iron (III) chloride in a molar ratio of less than 0.5, which is directly converted to vinyl chloride. You can. The molar ratio can be very advantageously performed by observing, for example, equipment and energy consumed by evaporating a portion of the EDC in a blow tank.

Description

Method for preparing 1,2-dichloroethane and apparatus for performing such method

In the so-called direct chlorination process, 1,2-dichloroethane (hereinafter referred to as EDC) is produced by reacting ethylene and chlorine. This addition reaction is catalyzed by metal halides that act as Lewis acids and halides of the Group 1 metals of the Periodic Table of the Elements.

In the method described in NL-A 6990198, the metal halide with Lewis acid behavior is preferably iron (III) chloride. The Group 1 metal of the periodic table of the elements is preferably a metal having an atomic number of 12 (sodium) or less, in particular lithium. The molar ratio of the halide having Lewis acid behavior and the halide of the Group 1 metal of the periodic table of elements is from 1: 2 to 2: 1.

EP 0 111 203 B2 describes a process wherein the catalyst used is anhydrous tetrachloroperate, for example sodium tetrachloroperate, or the corresponding component is used in stoichiometric amounts. In DE 4 103 281 Al the catalyst used is iron (III) chloride mixed with sodium chloride in a molar ratio of 1: 1.5 to 1: 2.

DE 4 103 281 Al discloses a process for direct chlorination in EDC as a solvent in the temperature range of 30 to 100 ° C., including the use of iron (III) chloride mixed with sodium chloride in a molar ratio of 1: 1.5 to 1: 2. It is. In the comparative example, this molar ratio is 1: 0.33, but in this case a relatively large amount of the undesired product, 1,1,2-trichloroethane, is obtained.

EP-A 0 075 742 discloses direct chlorination comprising introducing the reactants into a circulating liquid medium and thoroughly mixing in a mixing zone, followed by reacting the mixture in a reaction zone of about 75 to 200 ° C. and about 1 to 15 bar. Methods and apparatus therefor are described. A portion of the liquid reaction mixture is taken from the reaction zone and split into two parts of a stream, one of which is passed through the heat exchanger into the mixing and reaction zone and the other is fed to the expansion vessel. The vapor from this expansion vessel is passed through a fractionation column while the unvaporized liquid portion is returned to the mixing and reaction zones.

It has now been found that the direct chlorination reaction of ethylene proceeds particularly advantageously when the molar ratio of sodium chloride to iron (III) chloride remains below 0.5 during the entire reaction. Maintaining these conditions allows the reaction to proceed in such a way that, without distilling off the high boiling water, the EDC is produced with a purity high enough to be used directly to prepare vinyl chloride. In addition, the method of the present invention is not very expensive in terms of apparatus and energy consumption. Preferred aspects and related advantages of the present invention will be described in more detail below.

The reaction medium used is advantageously a liquid EDC and the reactants are fed into the circulating EDC. Here, the process of the invention does not need to use chlorine in liquid form, since the process can be carried out in gentle conditions under which gaseous chlorine can be used, especially at low pressures. The pressure is therefore advantageously at most 1 bar gauge pressure, preferably 0.4 to 0.6 bar gauge pressure, which is advantageously set using an inert gas blanket, preferably a nitrogen blanket.

Reaction temperature is 50-105 degreeC, Preferably it is 70-90 degreeC. Pressure and temperature are mutually adjusted such that the reaction is carried out below the boiling point of the EDC.

In a preferred embodiment of the invention, all or preferably only part of the EDC is passed into an expansion vessel maintained under vacuum, and the heat content of the EDC stream vaporizes part of the EDC. The vaporized EDC contains no catalyst and has a purity of at least 99.9% after condensation, so that it can be directly cleavage reaction to form vinyl chloride. This is necessary to remove the catalyst in a conventional process, so that it can be carried out without pressure drop or EDC vaporization and subsequently eliminates water washing which requires distillation drying of the EDC.

The pressure in the expansion vessel is advantageously 0.2 to 0.7 bar (absolute). This pressure reduction is generated and maintained using conventional fans or pumps (hereinafter referred to as vacuum pumps). If this vacuum pump is also not used to transport the gaseous EDC, the gaseous EDC is condensed using a suitable apparatus (hereinafter referred to as a chiller) and collected from the vessel.

By using the heat of reaction to partially vaporize the EDC and keep the reaction temperature in the desired range, the need for coolant is substantially reduced.

The unvaporized portion of the EDC containing the catalyst remaining in the expansion vessel is returned to the EDC circuit. This is possible because the reaction forms a very small proportion of byproducts and the EDC carrier contains only traces of hydrogen chloride.

The waste gas does not contain chlorine in particular. Particularly preferred process manners for passing a portion of the EDC, preferably a relatively small amount, into the expansion vessel have the further advantage of not requiring a second reactor for the conversion of residual ethylene. However, it is possible to provide such a device even in the preferred embodiment of the present invention because the device for removing and recycling it is not very expensive.

Thus, the ethylene-containing expansion vessel waste is preferably returned to the reactor from the downstream point of the vacuum pump by using a compressor, preferably a liquid jet compressor, suitable for mounting at the bottom of the reactor to re-react ethylene with chlorine. The ethylene yield can be further increased or the ethylene loss can be further reduced. Preferred drive jets for the compressor are advantageously the discharge stream (partial stream) of the circulating EDC.

However, the residual amount of ethylene can also be used to produce energy by waste incineration, preferably to recover hydrogen chloride.

Thus, the present invention also provides a device particularly suitable for the method of the present invention. This, along with its preferred embodiment, is shown in the figure.

The apparatus of the present invention comprises a reactor (1); Ethylene feed line (2); Chlorine supply line 3, preferably inert gas supply line 4; Decompression with a line 7 for separating the vaporized product and preferably via a pump 10 and preferably with a dissolution vessel 9 connected and a line 8 for conveying the unvaporized product. A line 5 connected to the expansion vessel 6 underneath; And preferably a line 11 for conveying the product partial stream passing through the pump 12 and the cooler or heat exchanger 13.

The line 7 for the EDC steam advantageously reaches the vacuum pump 15 via the cooler 14. Line 16 starts from cooler 14 and reaches liquefied EDC collector 17.

Advantageously, the apparatus of the present invention also provides a line 18 starting from the pressurization side of the vacuum pump 15 and reaching the reactor 1 via the compressor 19 to convey the residual amount of unreacted ethylene. It includes. Line 20 and line 21 are waste line disposal lines.

If the process is carried out for a long time, the ratio of sodium chloride to iron (III) chloride according to the invention should be maintained. Thus, for example, when iron (III) chloride is introduced into the plant, for example in a corroded state, a corresponding amount of sodium chloride should conveniently be metered out from the dissolution vessel 9, otherwise distillation This is because the purity of the separated EDC is reduced or by-product formation is increased.

Circulating EDC is transparent with an average purity of over 99%. That is, solid particles are not detected and are only slightly colored. Therefore, it is not necessary to discharge part of the stream to remove impurities.

The following examples illustrate the invention.

Examples 1-4

The direct chlorination reaction is carried out in reactor 1 with a volume of 14.6 m 3 and a charge volume of 81 vol%. The pressure is maintained at 0.54 bar gauge pressure by line 4 and the temperature at 75 ° C. The reaction medium is a liquid EDC containing 700 ppm of iron (III) chloride.

Sodium chloride is metered into the reaction medium through the dissolution vessel 9 until the molar ratio of sodium chloride to iron (III) chloride is desired (see the following table). The molar ratio is maintained throughout the reaction. The reactor 1 is fed via line 2 with ethylene 2000 standard m 3 / h and the corresponding amount of gaseous chlorine via line 3. The product discharge stream (partial stream) is introduced via line 5 into downstream expansion vessel 6 with an absolute pressure of 0.3 bar. Here, 8,90 tons of EDC are vaporized and discharged via line (7). This EDC contains no catalyst and has the purity shown in the table, which allows the EDC to be processed directly into vinyl chloride. The amounts of by-product 1,1,2-trichloroethane are also shown in the following table.

Unvaporized EDC remaining in expansion vessel 6 is returned to reactor 1 via line 8 and pump 10. The main product stream is fed to line (8) via line (11) and pump (12) and, if necessary, returned to reactor (1) via cooler (13).

In the table, Example 1 is a comparative example (without NaCl) and Examples 2 to 4 are examples according to the invention.

table

Claims (9)

A method for producing 1,2-dichloroethane by reacting ethylene with chlorine in the presence of a sodium chloride-iron chloride (III) catalyst, wherein the molar ratio of sodium chloride to iron chloride (III) is 0.3 or more and 0.5 during the whole reaction. Characterized by keeping it below. The method of claim 1 wherein the molar ratio of sodium chloride to iron (III) is in the range of 0.3 to 0.45. The process according to claim 1 or 2, wherein the reaction is carried out at 50 to 105 ° C. The process according to claim 1 or 2, wherein the reaction is carried out at a pressure below 1 bar gauge pressure. The method of claim 4, wherein the gauge pressure is set by an inert gas blanket. The process according to claim 1 or 2, wherein all or part of the 1,2-dichloroethane is introduced into a vessel maintained under reduced pressure, the distilled product is separated and the remaining 1,2-dichloroethane is returned to the reaction process. Way. The process according to claim 1 or 2, wherein the reaction medium is 1,2-dichloroethane. The process according to claim 1 or 2, wherein chlorine is supplied as a gas. Reactor 1; Ethylene feed line 2; Chlorine supply line 3; An inert gas supply line 4 connected to the reactor 1; A line 5 connected to an expansion vessel 6 having a line 7 for separating vaporized product and a line 8 for conveying unvaporized product; A dissolution vessel 9 connected to the line 8; A pump 10 located in line 8; A line 11 for returning a partial stream of product to the reactor 1; A pump 12 located in line 11; A cooler or heat exchanger 13 between the pump 12 and the reactor 1; A cooler 14 located in line 7 which is the starting point of line 16 reaching the 1,2-dichloroethane collector 17; Located in line 7, a vacuum pump 15 downstream of the cooler 14; A line 18 starting from the vacuum pump 15 and reaching the reactor 1 via the compressor 19; And waste line (20) and (21).